Hop pesticide review – Horticultural mineral oils- Cheap but effective in the hopyard.

Refined horticultural mineral oils go by many names - - dormant oil, summer oil, paraffinic oil, crop oil, stylet oil, white oil, etc.   All oils can be sprayed alone or with other compatible pesticides and have a direct contact mode of action on labelled pests and fungi. Oils direct contact action means very little possible resistance issues compared to many other pesticides. They are an inexpensive, safe, effective, and easy-to-use control for a quick knockdown of pests and pathogens like spidermites and mildew. Applied as a fall dormant spray it eliminates possible overwintering insect and mite eggs and fungal spores and mycelium. (Great as a post-harvest treatment going into late fall.) Crop oils also enhance weed control when combined with several different broadleaf and grass herbicides.  These oils are commonly used in field crops, orchards, and vineyards and should be in every hopyards arsenal of controls. They are considered to be a relatively soft control on beneficial insect populations, but should not be applied during beneficial insects active hours – Example: during bees foraging hours.

Horticultural oils to have a couple of important features that are necessary to understand before purchasing or applying them.  Mineral crop oils are refined with different weights; from very light and thin viscosities to heavier oilier types -  very similar to different grades of automotive oils.  They have the majority of sulfates removed to reduce crop burn potentials; but all have the ability to severely damage hops if used incorrectly.  The general rule of thumb is to select a thinner grade oil the hotter the day temperature is. (light summer oils vs. heavier Avoid application to the cone-bearing portions portion of hop plants and bines; as the oil will damage burrs and turn contacted cones brown. It is recommended to treat the lower non-coning portions of the hops near the ground to control populations of mites and mildews that tend to spread upward as the season progresses.

dormant oils).  Spraying these crop oils should be done during the coolest part of the day or evenings. Morning spraying should be avoided if hot mid-day temperatures are expected to climb above 80 degrees. 

Some manufacturers have obtained both labelling for hops and organic production.  Check the use labels carefully of different oils carefully to determine the proper grade and particulars of each product.

Some manufactures’ of horticultural crop oils are JMS Corporation, the Drexel Chemical Co., and Helena Chemical Corporation.

Blogged by hop grower Lynn Kemme / Great Lakes Hops    Fall 2015